The top American diplomat for Africa said Wednesday that some of the violence that has swept across Kenya in the past month has been ethnic cleansing intended to drive people from their homes, but that it should not be considered genocide.

Jendayi Frazer, the assistant secretary of state for African affairs, who visited some of the conflict-torn areas this month, said she had met with victims of the violence who described being ordered off their land.

“If they left, they were not attacked; if they stayed beyond the deadline, they were attacked,” said Ms. Frazer, while attending an African Union meeting in Ethiopia on Wednesday. “It is a plan to push people out of the area in the Rift Valley.”

The Rift Valley, one of the most beautiful slices of Africa, has been the epicenter of Kenya’s postelection problems and is home to ethnic groups that have long felt others do not belong.

The violence, fueled by decades-old tensions over access to wealth and power, exploded on Dec. 30, after the electoral commission said the incumbent president, Mwai Kibaki, won an election that observers said was deeply flawed. Ethnic groups like the Kalenjin, who were supporting Kenya’s top opposition leader, Raila Odinga, burned down homes and hacked to death Kikuyus, Mr. Kibaki’s ethnic group.